The Venice lagoon’s warm waters and sandy beaches have drawn tourists from around the world for hundreds of years.

Now, locals and visitors alike have one more spot to set up their deck chairs as a new island forms near the historic city.

Previously, the secret islet of Bacan would only form in the summer months before being swept away by winter’s storm surges.

But thanks to a new flood barrier this cherished refuge for tourist-shy residents has become a permanent fixture of the lagoon with its own flourishing ecosystem.

Measuring 250 metres long and 10 metres wide, the sandbank is covered with a layer of thick vegetation.

Bacan is now home to a range of marsh plants like samphire, rushes, native flowers, and small, salt-resistant cedars called tamarisk.

With new roots holding the soil in place, the island has not vanished since 2020 when the flood barrier’s operators were away on holiday during a winter surge.

However, even as residents celebrate the birth of a new beach, some experts warn that this could be a troubling sign for Venice’s fragile ecosystem.

In Venice’s shallow, brackish lagoon, small sandy islands can form from even slight disturbances to the swirl of the currents.

It takes so little for the tides to form a new island that residents of the area have a saying: ‘Palo fa palugo’ meaning ‘a pole makes an island’.

What made Bacan unique amongst this ever-changing archipelago was its seasonality.

In the warmer months as the water levels fell, Bacan would rise out of the waters where its quiet, inaccessible beaches made it a popular spot for residents of Castello, Venice’s southernmost neighbourhood.

Then, in winter, as the surges which so often flood the city arrive, the island would simply be washed away.

However, the islet remained resolutely above the waves for the entirety of the last four years.

According to Giovanni Cecconi, an engineer from the Università Ca’ Foscari in Venice, the island’s stability is a byproduct of the MOSE flood barrier which has protected the city since 2020.

The MOSE barrier, which Mr Cecconi worked on, is a series of mobile gates which rise up to separate Venice from the Adriatic Sea during winter surges.

Venice has always experienced floods when strong Sirocco winds combined with high tides to raise the water levels above the city streets.

However, in recent years, these periodical floods appear to be getting more common and more severe.

In 2019, one of the worst floods on record plunged 80 per cent of the city beneath water as sea levels rose 1.8m higher than normal.

The MOSE barrier helps avoid these deluges by temporarily sealing off the lagoon from the Adriatic when big surges are predicted.

However, a side effect is these powerful tides no longer wash away Bacan’s sands.

Mr Cecconi told The Times: ‘By raising the barrier in winter to stop high waters, the island is protected from the surges that used to erode it.

The location of the island may also explain why it has grown so much since MOSE was implemented.

Located opposite one of the three lagoon entrances fitted with flood defences, Bacan may benefit from an increased current during the summer months.

Mr Cecconi says: ‘The barrier … accelerates the flow of water into the lagoon when it is open, meaning more sand comes in, helping sustain Bacan.’

And as the island becomes populated by vegetation, its soils will become further stabilised, making it more likely to survive future erosion.

‘It is a new ecosystem and shows that the lagoon can evolve in a positive way in parallel with human intervention,’ Mr Cecconi adds.

However, not every expert is convinced by Mr Cecconi’s explanation.

Professor Adrea D’Alpos, an expert on the evolution of coastal areas from the University of Padua, told MailOnline that it is a mistake to attribute Bacan’s formation entirely to MOSE closures.

He says: ‘The development of this narrow strip of sand and mud, now colonized by vegetation, is primarily the result of several overlapping processes acting across different spatial and temporal scales.’

Furthermore, Professor D’Alpos points out that Bacan’s formation actually began well before the first MOSE activation in October 2020.

This means that the flood barriers surrounding the city are likely to be only part of a bigger and more complex picture.

Nor is Professor D’Alpos convinced that Bacan will become a year-round beach spot for future generations of Venetians.

He says: ‘I would not describe it as permanent. While the islet is currently accreting and its elevation is now above mean sea level, its persistence over the long term remains uncertain.’

Critically, Professor D’Alpos also argues that the development of a burgeoning ecosystem on Bacan is not necessarily a sign that nature is recovering.

While the MOSE flood barrier is indispensable for Venice’s survival, it is also having a profound effect on the surrounding environment.

Most importantly, by preventing high tides from washing over the land, the barrier stops sediment from being carried out to the salt marshes surrounding the city.

‘Although MOSE activations are essential for protecting Venice from high tides, they drastically reduce the tidal peaks during storm surges and significantly limit the extent and duration of salt marsh flooding,’ Professor D’Alpos says.

‘This, in turn, diminishes sediment deposition on the marshes, threatening their long-term survival.’

Studies have shown that Venice’s salt marshes owe 70 per cent of their growth to these winter storm surges.

Venice’s salt marshes have been slowly vanishing for centuries, partly due to historic waterway mismanagement dating back to the 1500s when water was diverted away from the lagoon. 

Since salt marshes absorb 30 times as much CO2 as a forest, their disappearance would be a big deal for the planet.

And, since the salt marshes buffer the impact of storm surges and reduce flooding, anything that limits their extent will also be a big deal for Venice itself. 

So, while the new life on Bacan might be good news for beachgoers, it could be a sign of some worrying changes to come.